This invention relates to an apparatus and method for winding coils and for inserting the coils in the slots of the stator core.
More specifically the invention pertains to an apparatus and method for winding stator coils of relatively thick wire, one coil at a time, to retain the completed coils on a placer tooling apparatus while winding of the complete set of stator coils is completed and then to insert all of the coils simultaneously into the slots of a stator core. The invention is particularly adapted for winding and placement of alternator stator coils for automotive applications.
Alternators for automotive applications require stator coils of relatively heavy wire. While equipment for winding coils and inserting coils into the axial slots of stator cores is well known in the prior art, several problems have been encountered in applying prior art coil winding and inserting equipment to the construction of alternator stators. The heavy wire of which the coils are constructed has a diameter which is almost equal to the size of the gaps which separate the stator core teeth. Conventional insertion equipment has utilized coil inserting blades which have lips to shield the sharp edges of the teeth adjacent the gaps so that the wire, during insertion through the iron gaps, is not damaged. However, when coils are constructed of such heavy wire, the protective blade lips close off too much of the iron gaps and thereby prevent the wire from entering the gaps, or alternatively cause damage to the wire if it is forced through the gaps during insertion.
Furthermore, prior art placer tooling has used slender blades which span only a single tooth each. The slender blades are distorted by the insertion of relatively heavy wire into the stator core slots, thereby preventing proper alignment of the stator core slots with the coils as they are being inserted and resulting in damaged coils.
Another problem with prior art coil winding and insertion equipment has been that coils constructed of heavy wire are distorted during winding. As the successive coils are being wound, one coil at a time, the completed coils must be retained on the insertion blades as the equipment completes winding of the complete set of coils and prior to insertion of the coils into the stator core. As the equipment indexes after completion of each coil, the relatively heavy wire is pulled so tightly against the blades that the shape of the coil is distorted. Additionally the wire may be damaged as it is drawn up tightly against the outsides of the blades.
It is therefore desired to provide insertion equipment wherein retaining devices are employed for retaining the completed coils and wherein the retaining devices are located outside the insertion blades so that the wire, as it is pulled from a completed coil to the next coil to be formed, does not exert distorting forces on the coil blades and the completed coil retains its desired shape.
In some prior art equipment clamping mechanisms have been provided to clamp the wire after completion of a coil, thereby preventing coil distortion since the wire is pulled against the clamping force as the equipment is indexed to the next coil forming station. These clamping arrangements have several disadvantages. First of all the clamps may cause the wire to be damaged or nicked because of the relatively high clamping forces necessary. Secondly because a fairly long length of wire is required to be held by the clamp, loops of wire are formed between successive coils. These loops of wire need to be tucked in after insertion of the coils into the stator core. Not only is the need for such wire loops costly in terms of materials but, most importantly, the loops require additional labor to handle, add cycle time to the process and add extra weight to the stator.
What is therefore desired is the elimination of clamping devices and the provision of equipment wherein no clamps are necessary to clamp the wire after completion of each coil. It is furthermore desired to eliminate the need for loops of wire between successive coils and to eliminate damage to the coil wire as it is being wound.
Prior art equipment has generally utilized bore blocks for insertion of coils into alternator stator cores. Such devices are cylindrical in shape and are sized to fit into the stator core bore. The bore block includes radial coil holding slots arranged around its periphery. After the bore block is inserted into the stator core the coils are ejected from the holding slots and are inserted into the stator slots.
In today's energy conscious society there is a constant need to reduce the size and weight of automobiles and to conserve space and weight in automobile engine compartments. Manufacturers of automotive equipment have therefore been under pressure to reduce the weight and size of components to be housed in the engine compartments. It is therefore desired to make very compact alternators. The reduction in the size of alternators has been carried to the point where the coil holding slots in bore blocks have reached their coil holding capacity. Bore blocks can therefore not be further reduced in size and alternators cannot be further decreased in diameter. It is therefore desired to provide insertion equipment for inserting alternator stator coils into stator cores without the use of a bore block so that the diameter of the alternators can be further reduced.